This invention relates to a bead lock apparatus incorporating in a tire building apparatus and a bead lock method for locking a bead ring by using the bead lock apparatus, and more particularly to a method for properly holding a bead ring without causing its deformation or eccentricity in fixing the bead ring to a tire forming drum at a predetermined position thereon.
So-called positive or negative type bead lock apparatuses have been known which incorporate in a tire building apparatus receiving bead rings from the bead lock apparatuses onto a forming drum at predetermined positions thereon.
In the positive type bead lock apparatus, a cylindrical band is expanded only at its center portion of its length, and a bead ring held by a bead setter is then delivered from the setter onto the cylindrical band at the boundary position between the expanded portion and the remaining portion of the band.
In the negative type bead lock apparatus, on the other hand, a bead ring held by a bead setter is positioned around the outer circumferential surface of a band held with a uniform diameter on a forming drum, and the bead ring is then delivered onto a plurality of bead lock segments expansible and contractible at predetermined positions.
With the positive type bead lock apparatus, a bead ring is held by the bead setter composed of a plurality of expansible and contractible pawl members circumferentially spaced predetermined distances from each other and engaging the inner circumferential surface of the bead ring. Therefore, this type lock apparatus has an advantage in that the bead ring can be sufficiently properly held without causing any deformation or the like.
However, when the bead ring is delivered onto the band at the boundary position between the expanded portion and the remaining portion of the band on a tire building apparatus, the bead ring is likely to move to be eccentric to the axis of a forming drum due to wrinkles occurring at the boundary position of the band. Moreover, reinforcing cords in the band become nonuniform in circumferential directions due to the wrinkles, and an extra process step is needed for expanding the band at the center portion of the length to complicate the production processes.
With the negative type bead lock apparatus, on the other hand, as a bead ring is delivered onto a band held in a cylindrical form having a uniform diameter, it is possible to eliminate the disadvantages due to the expansion of its center portion described above.
In the negative type bead lock apparatus, however, the bead lock segments are brought into engagement with the inner circumferential surface of the bead ring by expanding the bead lock segments to increase their diameter. Therefore, the bead ring cannot be held by the bead lock segments under the state that the bead ring is held by the bead setter in engagement with the inner circumferential surface of the bead ring. Consequently, deformation or eccentricity of the bead ring cannot be avoided when the bead lock segments are brought into engagement with the bead ring.